BY FRANKLIN MATTHEWS.  
II.
 
Just outside the door of the Captain's cabin, on every ship of the navy, there stands a sentry. He paces up and down for a distance of about ten feet. On one of the sides of the cabin is an electric indicator similar to those seen in the large hotels back of the clerk's desk. The sentry on the ship passes that indicator every time he paces from one end of his limited beat to the other. He cannot escape hearing its bell when it rings, and his eye at once sees whence the signal comes that is telegraphed to the Captain in time of emergency. That indicator is placed there so that, when necessary, there shall be instant communication with the Captain. Some of the dials tell stories of the utmost importance to the safety of the ship. They tell these stories automatically.
Let us see how one of the most important of these dials may perhaps save the ship from destruction. Down in the coal-bunkers there is a little instrument attached to the side of each compartment that looks like a little thermometer. It is not more than four or five inches tall. It is simply a thermometer with an electric attachment. A fire has started in a coal-bunker, as happens sometimes on large steamships, through what is known as "spontaneous combustion." It may smoulder for several days and give no indication of its existence. At last it breaks into a flame. Some one has felt a hot deck through his shoes as he has walked along, or perchance has accidentally placed his hand on the iron-work of the compartment and found it blistering hot. Instantly the fire-alarm is rung, and if the fire is not too far advanced the ship may be saved. On war-ships, however, no such risk must be run. In the economy of space on such ships it frequently happens that these coal-bunkers are placed very near, and sometimes next to, the powder-magazines. A fire in the coal-bunkers would mean an awful explosion, the loss of the ship and hundreds of lives.
Here is where that little thermometer plays its heroic part. It is called a thermostat, and it is so arranged that as the heat increases, the mercury in the bulb slowly rises to what is known as the danger-point. When the heat reaches that point the mercury sets an electric current going. At once the bell on the indicator where the sentry outside the Captain's door stands rings violently. The sentry hurries to it and sees a fire-alarm from a certain compartment, and he hastily awakes the Captain. The latter presses a button, perhaps without getting out of bed or up from his chair, and instantly there rings the general fire-alarm throughout the ship, and every man on board is called to quarters. For a few seconds it is time of immense confusion and noise. Great gongs are ringing in various parts of the ship. Men are hurrying half dressed, if it be in the night, here and there, and there is much shouting in the giving and passing of orders. In a twinkling, however, order prevails, and through the aid of that little automatic thermometer the ship and the lives of those on board are saved. This thermostat is an insignificant-looking affair—a mere trifle in the ship's construction—but see what an important thing it really is. These instruments are used in many buildings on land, but nowhere are they of such importance as when placed in coal-bunkers or on the outside walls of magazines in war-ships.
Another dial on the indicator where the sentry paces also plays an important part in war-ships. It is called the water-alarm. All modern war-ships have what are known as double bottoms. They are built to prevent the ship from sinking or from becoming flooded in the chief compartments of the vessel below the water-line. Sometimes a ship may scrape along the top of an unknown rock or reef, or may strike some obstruction floating unseen beneath the waves. No one on board may feel the shock, especially if it is a light one. The water may rush into one of these double bottoms, and although the ship may be safe from sinking, the danger in time may be most grave. As the water fills the compartment which has been broken, a little piece of wood rises with it, and finally, when it reaches a certain height, it too establishes an electric current, and the alarm rings outside the cabin door of the Captain. Again the alarm sounds through the ship, and if possible, the break is mended temporarily, and the pumps set going to clear the compartment of the water.
A TORPEDO BURSTING AN OUTER COMPARTMENT.
In time of battle, however, this water-alarm may tell a more important story. Perhaps a torpedo from the enemy has struck the ship, and a gaping wound has been torn not only in the outside bottom of the ship, but through the inner hull as well. Instantly the news reaches the Captain through the water-alarm. The Captain simply presses a button, and at once not only does the general alarm ring, but the "siren" whistle on the ship is set to shrieking most horribly. Those siren whistles are seldom heard either in port or at sea. They begin their noise with a low[Pg 89] moan, and run up to an awful shriek, with a thin, ear-piercing note that is almost unendurable. The siren may be blown by electricity as easily as an electric door-bell may be rung. When the siren is heard it is a signal throughout the ship to close all the water-tight doors in the various compartments, and thus confine the inrushing waters to a limited space. If only one or two compartments are torn open by the torpedo, the ship may be saved from sinking and a great tragedy of war may be averted. When the siren howls, however, there is such a scurrying on shipboard as is never seen at other times. Nearly every compartment has men in it at work. The alarms and the whistles are their only warning, except, perhaps, the shouts of their companions. A mighty rush is made to get out of some of these compartments. No time must be lost, and there can be no waiting for a man to escape. If shut in, he may be drowned. It is a question of his life or that of the ship and the lives of the rest of the crew, and there is only one way to answer that question.
These water-alarms are used in many large buildings in connection with the fire-alarm, but one can see how much more important they are on ships, especially on war-ships, than on land. They are a most simple contrivance, and, like the thermostat, mere trifles; but they may turn the tide in a naval battle, and directly or remotely settle the fate of a nation.
In the early days of steam navigation the Captain of a vessel could speak to the engineer through a tube and regulate the speed of the ship. When the vessels grew larger, the signalling was done by means of bells. That method is in common use to-day in many vessels that ply in harbors, such as river steamboats and tug-boats. As the ocean-liners increased in size the bell system of signalling became antiquated. The Captain or the navigator was 300 or 400 feet away from the engineer, and from 20 to 40 feet above the engine-room. In time of emergency it became necessary to send word to the engineer exactly what to do in half a dozen different cases. He must stop, back, go slow now with one engine and now with another, or with both. A long chain was run from a contrivance on the bridge to the engine-room. When the Captain pressed forward or backward a handle on a vertical dial, a handle in the engine-room would move on a similar dial, and a bell would ring to call attention to it, and the engineer knew at once what to do. This system is in use at the present time on all large passenger-ships and most war-ships in the world.
Electricity has invaded this f............